Method of controlling intake manifold pressure during...

Details Method of controlling intake manifold pressure during... Method of controlling intake manifold pressure during...

2000-01-11

2001-05-22

Solis, Erick (Department: 3747)

Internal-combustion engines

Combustion chamber means having fuel injection only

Having a particular relationship between injection and...

C123S305000, C123S491000, C123S179160, C123S179180

Reexamination Certificate

active

06234141

ABSTRACT:

TECHNICAL FIELD
This invention relates to engine control systems and, more particularly, to a method of controlling intake manifold pressure during startup of a direct injection engine.
BACKGROUND OF THE INVENTION
Direct injection engines nominally operate at a higher fuel pressure (typically 5-12 Mpa) than other gasoline engines and the fuel injectors are accordingly sized for this higher pressure. When a direct injection engine is started, the fuel pressure is below the nominal value, and the pressure is limited to that supplied by a low pressure (typically electric) pump. Since the fuel pressure during engine starting is initially so much lower than the pressure available from the mechanical pump used for normal operation, long injector pulse widths are necessary to deliver the required fuel mass. Also, since the fuel is injected directly into the cylinder, the injection must be complete before the increasing cylinder pressure on the compression stroke exceeds the pressure in the fuel supply.
In typical engine control systems, an air bypass valve or electronic throttle is usually opened to a position that will allow sufficient air flow to quickly increase torque and allow the engine to reach an initial target high idle speed. This airflow helps maintain a higher intake manifold pressure during cranking and the initial start and allows the engine speed to rise rapidly once combustion is started. However, for the direct injection engine, a higher pressure in the manifold results in higher pressure in the cylinder and a smaller fraction of the compression stroke being available for fuel injection. Also, as the engine speed increases, the time available for fuel injection during any given portion of an engine cycle (typically the intake stroke and the first part of the compression stoke) is reduced. On the other hand, targeting a lower intake manifold pressure results in a smaller cylinder air charge, thereby requiring a correspondingly smaller mass of fuel to be injected at a given air/fuel ratio.
SUMMARY OF THE INVENTION
In accordance with the present invention the air flow into the intake manifold is limited so that the manifold air pressure is reduced during engine cranking and starting. Once the engine is started, the air flow is limited to the amount which gives stable combustion until sufficient fuel pressure is available to allow the fuel mass to be injected with a pulse width that conforms to the reduced time available at the higher engine speeds. The present invention calculates the maximum fuel flow based on fuel pressure and the injector characteristics. The engine combustion process has a “lean” air/fuel ratio limit which is scheduled as a function of engine coolant temperature and engine run time. The maximum air flow limit is determined from the maximum fuel flow and the “lean” air/fuel ratio limit, but may be chosen to be less than this, and the throttle is adjusted to achieve this target.
More particularly, in accordance with the present invention, the air flow in the intake manifold of a direct injection engine, during starting, is limited, based on a desired air/fuel ratio (AFR) and a maximum available fuel flow rate. The desired AFR is less than or equal to the leanest AFR that delivers stable combustion during engine starting conditions. The maximum available fuel flow is based on a determination of the maximum available fuel pulse width, fuel pressure, and engine rotation time period based on engine speed. The fuel pulse width is the time interval between the start and end of injection, the latter of which should occur before the ignition time and before the pressure crossover point where an estimate of cylinder pressure during compression surpasses the fuel injection pressure. The start of injection can be advanced during starting as a function of fuel pressure to maximize the available fuel pulse width. The method of the present invention permits a decrease in instantaneous cylinder pressure by reducing intake manifold pressure thereby increasing the time available for fuel injection during the compression stroke, which allows sufficient fuel to be injected at the lower fuel pressures present during starting of a direct injection engine. Also, this invention will prevent fuel from being injected for particular engine cycles when it is estimated that the limited fuel quantity that could be injected might result in an air/fuel ratio that is likely to cause a misfire.


REFERENCES:
patent: 3960130 (1976-06-01), Peterson, Jr.
patent: 4693222 (1987-09-01), Itou et al.
patent: 4987871 (1991-01-01), Nishikawa
patent: 5322044 (1994-06-01), Maebashi
patent: 5676101 (1997-10-01), Kawai et al.
patent: 5704324 (1998-01-01), Ichinose et al.
patent: 5718203 (1998-02-01), Shimada et al.
patent: 5732675 (1998-03-01), Yoshida et al.
patent: 5735241 (1998-04-01), Matsuura
patent: 5806497 (1998-09-01), Hosoya
patent: 5873344 (1999-02-01), Kudou et al.
patent: 5894828 (1999-04-01), Sivashankar et al.
patent: 5910096 (1999-06-01), Hepburn et al.
patent: 5947078 (1999-09-01), Fujiwara
patent: 5970955 (1999-10-01), Nakada
patent: 6050232 (2000-04-01), Grob et al.

Affiliated with

Also associated with

Rating

Method of controlling intake manifold pressure during... does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Method of controlling intake manifold pressure during..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of controlling intake manifold pressure during... will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2475902